Hormonal response to competition among male coalitions

Previous research has shown that testosterone (T) and cortisol (C) are released in response to a wide variety of social stimuli including dyadic (one on one) competitive events, but humans also compete as groups. Here we report results from a pilot study of hormonal responses to competition between male coalitions. Salivary T and C levels were assessed in adult males from a rural Caribbean village who competed at dominoes, as two-man teams, against (a) familiar men from their own village (within coalition), and (b) strangers from another village (between coalitions). Analyses indicate that both T and C levels were higher and responses more pronounced for between-village competition than for within-village competition, but we could not compare responses to victory and defeat in the between-village case, since our subjects happened to win both such contests. Further studies of endocrine responses in the context of coalitional competition are warranted.     

Sex difference in testosterone response to a video game contest

Testosterone (T) and cortisol (C) were assayed from saliva samples given by young men (n = 28) and women (n = 32) before, during, and after competing with a same-sex partner in a video game. The T response to the competition is different in each sex; the C response is the same. Male results confirm prior reports of a precontest rise in testosterone. Male results did not confirm previous findings that, after a contest, the testosterone of winners is higher than that of losers, perhaps because the video game contest produced little mood difference between male winners and losers. Unlike male testosterone, female testosterone generally decreased throughout the experiment. Trends in T and C are parallel in women but not in men. Apparently T works differently in competition between men than between women.     

Testosterone and cortisol jointly regulate dominance: Evidence for a dual-hormone hypothesis

Traditional theories propose that testosterone should increase dominance and other status-seeking behaviors, but empirical support has been inconsistent. The present research tested the hypothesis that testosterone's effect on dominance depends on cortisol, a glucocorticoid hormone implicated in psychological stress and social avoidance. In the domains of leadership (Study 1, mixed-sex sample) and competition (Study 2, male-only sample), testosterone was positively related to dominance, but only in individuals with low cortisol. In individuals with high cortisol, the relation between testosterone and dominance was blocked (Study 1) or reversed (Study 2). Study 2 further showed that these hormonal effects on dominance were especially likely to occur after social threat (social defeat). The present studies provide the first empirical support for the claim that the neuroendocrine reproductive (HPG) and stress (HPA) axes interact to regulate dominance. Because dominance is related to gaining and maintaining high status positions in social hierarchies, the findings suggest that only when cortisol is low should higher testosterone encourage higher status. When cortisol is high, higher testosterone may actually decrease dominance and in turn motivate lower status.     

粪便激素水平反映不同出生时期雄性布氏田鼠的繁殖策略

布氏田鼠是我国内蒙古草原的主要害鼠之一,具有明显的季节繁殖特征,不同季节出生个体可能具有不同的繁殖策略,但尚缺乏内分泌证据支持。本研究采用标志重捕法,连续监测大型自然围栏中不同年龄雄性布氏田鼠的繁殖状态和应激水平的季节变化,分析各年龄组雄鼠的繁殖发育策略。结果表明,越冬雄鼠可保持较高的睾丸下降率和睾酮水平至8月初;而部分5月生雄鼠的繁殖期睾酮水平较接近越冬鼠,但8月初已降至年内最低水平,而6月及以后出生雄鼠睾酮始终处于较低水平;这说明越冬鼠的繁殖状态可贯穿繁殖期始终,只有部分5月生雄鼠可能参与当年繁殖,而6月及以后出生雄鼠则不能在当年繁殖。越冬鼠皮质醇水平高于当年鼠,繁殖期高于非繁殖期,这可能是越冬鼠由于繁殖需要而保持较高应激状态,从而造成繁殖盛期后死亡率升高。这些结果说明,不同时期出生的雄性布氏田鼠具有不同的出生后性腺发育模式和繁殖策略,反映出生存与繁殖之间的权衡。     

Effects of heavy resistance training on maximal and explosive force production, endurance and serum hormones in adolescent handball players

To determine the effects of 6-weeks of heavy-resistance training on physical fitness and serum hormone status in adolescents (range 14-16 years old) 19 male handball players were divided into two different groups: a handball training group (NST, n = 10), and a handball and heavy-resistance strength training group (ST, n = 9). A third group of 4 handball goalkeepers of similar age served as a control group (C, n = 4). After the 6-week training period, the ST group showed an improvement in maximal dynamic strength of the leg extensors (12.2%; P < 0.01) and the upper extremity muscles (23%; P < 0.01), while no changes were observed in the NST and C groups. Similar differences were observed in the maximal isometric unilateral leg extension forces. The height of the vertical jump increased in the NST group from 29.5 (SD 4) cm to 31.4 (SD 5) cm (P < 0.05) while no changes were observed in the ST and C groups. A significant increase was observed in the ST group in the velocity of the throwing test [from 71.7 (SD 7) km x h(-1) to 74.0 (SD 7) km x h(-1); P < 0.001] during the 6-week period while no changes were observed in the NST and C groups. During a submaximal endurance test running at 11 km x h(-1), a significant decrease in blood lactate concentration occurred in the NST group [from 3.3 (SD 0.9) mmol x l(-1) to 2.4 (SD 0.8) mmol x l(-1); P < 0.01] during the experiment, while no change was observed in the ST or C groups. Finally, a significant increase (P < 0.01) was noted in the testosterone:cortisol ratio in the C group, while the increase in the NST group approached statistical significance (P < 0.08) and no changes in this ratio occurred in the ST group. The present findings suggested that the addition of 6-weeks of heavy resistance training to the handball training resulted in gains in maximal strength and throwing velocity but it compromised gains in leg explosive force production and endurance running. The tendency for a compromised testosterone:cortisol ratio observed in the ST group could have been associated with a state of overreaching or overtraining.     

Short-term changes in fathers' hormones during father-child play: impacts of paternal attitudes and experience

Hormonal differences between fathers and non-fathers may reflect an effect of paternal care on hormones. However, few studies have evaluated the hormonal responses of fathers after interacting with their offspring. Here we report results of a 30-minute in-home experiment in which Filipino fathers played with their toddlers and consider whether paternal experience and men's perceptions of themselves as fathers affect hormonal changes. Fathers provided saliva and dried blood spot samples at baseline (B) and 30 (P30) and 60 (P60, saliva only) minutes after the interaction. We tested whether testosterone (T), cortisol (CORT), and prolactin (PRL) shifted after the intervention. In the total sample, T did not vary over the study period, while CORT declined from B to P30 and P60, and PRL also declined from B to P30. Fathers who spent more time in daily caregiving and men who thought their spouses evaluated them positively as parental caregivers experienced a larger decline in PRL (B to P30) compared to other fathers. First-time fathers also had larger declines in PRL compared to experienced fathers. Experienced fathers also showed a greater decline in CORT (B to P60) compared to first-time fathers. These results suggest that males' paternal experience and age of offspring affect hormonal responses to father–child play and that there is a psychobiological connection between men's perceptions of themselves as fathers and their hormonal responsivity to childcare.     

Women's intercollegiate athletic competition: Cortisol,testosterone, and the dual-hormone hypothesis as it relates to status among teammates

Recent research suggests that testosterone and cortisol jointly regulate dominance motivation and, perhaps, the status relationships that are affected by it. For this article, the results of six different studies of women's intercollegiate athletic competition were combined to give a sample size of almost ninety women for whom we had before- and after-competition values for salivary cortisol and testosterone for at least one and sometimes two competitions. For many of these women, we had surveys that allowed us to assess their status with teammates. In no matter what sport (soccer, softball, volleyball, and tennis) levels of salivary cortisol and testosterone increased when women participated in athletic competition. Salivary levels of C and T appear to rise in parallel during competition and increases in levels of one hormone are significantly related to increases in the other. Salivary levels of these hormones typically decreased for teammates who did not play but watched the competition from the sidelines. For women who played in two competitions, individual differences in the positive effect of competition on cortisol and testosterone were conserved from one competition to the next, affirming the personal consistency of endocrine responses to competition. Status with teammates was positively related to before-competition levels of testosterone, but only for women with relatively low before-competition levels of cortisol. This result provides novel support for the “dual-hormone hypothesis” as it relates to predicting social status in women's athletic teams — natural social groups of individuals who know each other and whose social hierarchy has evolved over the course of practice and play for at least one and, in some cases, several years of intercollegiate athletic competition.     

Virtual navigation in humans: the impact of age, sex, and hormones on place learning

Certain cognitive processes, including spatial ability, decline with normal aging. Spatial ability is also a cognitive domain with robust sex differences typically favoring males. However, tests of spatial ability do not seem to measure a homogeneous class of processes. For many, mentally matching rotated three-dimensional images is the gold standard for measuring spatial cognition in humans, while the Morris water task (MWT) is a preferred method in the domain of nonhuman animal research. The MWT is sensitive to hippocampal damage, a structure critical for normal learning and memory and often implicated in age-related cognitive decline. A computerized (virtual) version of the MWT (VMWT) appears to require and engage human hippocampal circuitry, and has proven useful in studying sex differences and testing spatial learning theories. In Experiment 1, we tested participants (20-90 years of age) in the VMWT and compared their performance to that on the Vandenberg Mental Rotation Test. We report an age-related deficit in performance on both tasks. In Experiment 2, we tested young (age 20-39) and elderly (age >60) participants in the VMWT and correlated their performance to the circulating levels of testosterone and cortisol. Our findings indicate that the persistence of male spatial advantage may be related to circulating testosterone, but not cortisol levels, and independent of generalized age-related cognitive decline.     

Adrenal hormones mediate melatonin-induced increases in aggression in male Siberian hamsters (Phodopus sungorus)

Among the suite of seasonal adaptations displayed by nontropical rodents, some species demonstrate increased territorial aggression in short compared with long day lengths despite basal levels of testosterone. The precise physiological mechanisms mediating seasonal changes in aggression, however, remain largely unknown. The goal of the present study was to examine the role of melatonin, as well as adrenal hormones, in the regulation of seasonal aggression in male Siberian hamsters (Phodopus sungorus). In Experiment 1, male Siberian hamsters received either daily (s.c.) injections of melatonin (15 microg/day) or saline 2 h before lights out for 10 consecutive days. In Experiment 2, hamsters received adrenal demedullations (ADMEDx), whereas in Experiment 3 animals received adrenalectomies (ADx); control animals in both experiments received sham surgeries. Animals in both experiments subsequently received daily injections of melatonin or vehicle as in Experiment 1. Animals in all experiments were tested using a resident-intruder model of aggression. In Experiment 1, exogenous melatonin treatment increased aggression compared with control hamsters. In Experiment 2, ADMEDx had no effect on melatonin-induced aggression. In Experiment 3, the melatonin-induced increase in aggression was significantly attenuated by ADx. Collectively, the results of the present study demonstrate that short day-like patterns of melatonin increase aggression in male Siberian hamsters and suggest that increased aggression is due, in part, to changes in adrenocortical steroids.     

Sex hormones, central nervous system and pain

The aim of the present review, which highlights some relationships between sex hormones, the CNS and pain, is to provide reference points for discussion on one of the most intriguing aspects of pain pathophysiology: the presence of sex differences in the response threshold to phasic painful stimuli and in the incidence of chronic pain syndromes. The first part of the review deals with sex steroids and their mechanisms of action. In the second part, the connections between sex steroids, the CNS and pain are illustrated to introduce possible areas of discussion in the study of sex differences in experimental and clinical pain.     

Experimental test of the effect of maternal hormones on larval quality of a coral reef fish

Maternal hormones can play an important role in the development of fish larvae. Levels of the stress hormone, cortisol, in females are elevated by social interactions and transferred directly to the yolk of eggs, where they may influence developmental rates. In some vertebrates, prenatal exposure to high levels of testosterone determine early growth rates, social status and reproductive success. The present study examined whether post-fertilization exposure of eggs of the tropical damselfish, Pomacentrus amboinensis (Pomacentridae), to natural levels of cortisol or testosterone directly affects larval morphology at hatching. Maternal and egg levels of cortisol and testosterone varied widely among clutches of eggs from local populations around Lizard Island on the Great Barrier Reef. The morphology of larvae produced by these local fish populations also varied widely and differed significantly among sites (e.g., standard length: 2.6–3.4 mm; yolk sac area: 0.01–0.13 × 10⁻² mm²). Laboratory experiments showed that elevated cortisol levels in the egg reduced larval length at hatching, while slight elevations in testosterone increased yolk sac size. The influence of testosterone, and to a smaller extent cortisol, on larval morphology differed among egg clutches. These differences were partly explained by differences in initial egg hormone levels. Morphological changes induced by experimental hormonal regimes encompassed the entire range of variability in body attributes found in field populations. It is unclear whether cortisol influences growth alone or development rate or both. Testosterone appears to influence yolk utilization rates, and has no significant effect on growth, in contrast to its role in later developmental stages. Maternally derived cortisol and testosterone are important in regulating growth, development, and nutritive reserves of the embryo and larvae of this fish species. Factors that influence the maternal levels of cortisol and testosterone may have a major impact on larval mortality schedules and, therefore, on which breeding individuals contribute to the next generation. Received: 19 August 1998 / Accepted: 16 November 1998     

Cortical correlates of perception and suppression of electrically induced pain

Two neuroimaging studies using fMRI were conducted in order to assess the cortical processes involved in the perception and suppression of pain. In the first study, 15 healthy subjects were stimulated with variable intensities of electrical pulses during a discrimination task. In the second study, the same subjects had to try to suppress the feeling of pain during tonic stimulation. The discrimination task resulted in cortical activation of contralateral SI, corresponding in extent to the intensity of the stimulus. Activation of contralateral operculum/posterior insula (SII) and non-dominant dorsolateral prefrontal cortex (DLPFC) with non-painful stimuli changed to activations of non-dominant anterior insula upon painful stimulation. In the second study, all subjects succeeded in suppressing the feeling of pain during previously painful levels of stimulation. During this suppression task, activations changed from anterior to posterior insula; also there was a suppression of activity in the anterior cingulated cortex (ACC) and caudate nucleus. Subjects seem to be able to suppress to a certain degree the feeling of pain under constant (and previously painful) stimulation. The cortical correlate seems to be a shift of cerebral activation from anterior to posterior right insula and a suppression of activity in the ACC and caudate nucleus.     

Testosterone change after losing predicts the decision to compete again

Testosterone (T) levels can fluctuate after wins and losses, but surprisingly, there are no empirical studies in humans that have tested whether these post-competition T changes predict the social behaviors that follow. The present study examined whether changes in T after losing in a competition predicted who wanted to compete again in a second competition. Sixty-four males provided saliva samples immediately before and 15 min after a rigged one-on-one competition. After the second saliva sample, participants chose whether or not to compete again against the same competitor. Winners did not increase in T relative to losers, but pre-competition cortisol, change in cortisol, and pre-competition T were associated with T changes, especially in losers. Importantly, changes in T predicted decisions to compete again in losers. Losers who increased in T were more likely to choose to compete again than losers who decreased in T. T changes were unrelated to decisions to compete again in winners. These findings provide novel data in humans that T changes after a status loss predict subsequent social behavior. Our discussion focuses on the theoretical implications of these findings for the link between short-term T changes and status-related behaviors.     

Effect of neurogenic acupoint cupping on high sensitive C-reactive protein and pain perception in female chronic pelvic pain: A randomized controlled trial

Objectives:To determine the effect of neurogenic acupoint dry cupping therapy on high sensitive C-reactive protein (hs-CRP) level, pain perception & intensity, and life impact of pelvic pain in women with chronic pelvic pain (CPP), with regard to the biological and neurophysiological impacts of dry cupping on acupoint.Methods:Thirty women with CPP were randomly divided into two equal groups; the study group received dry cupping on neurogenic acupoints plus lifestyle modifications for 8 weeks (n=15), while the control group received only lifestyle modifications for 8 weeks (n=15). Women were assessed pre- and post-rehabilitation program with the hs-CRP blood test, the short-form McGill Pain Questionnaire (SF-MPQ), and the pelvic pain impact questionnaire (PPIQ).Results:Comparing both groups post-treatment revealed that there were significant reductions in levels of hs-CRP, and scores of SF-MPQ & PPIQ (p<0.05) in the study group compared with the control group. Also, there were significant positive correlations between hs-CRP and both SF-MPQ “Visual Analogue Scale (VAS), Present Pain Intensity (PPI) index & Pain Rating Index (PRI)” and PPIQ (p<0.05).Conclusion:Neurogenic acupoint cupping therapy had significantly improving effects on the degree of inflammation, pain perception & intensity, and life impact of pelvic pain in women with CPP.     

Sensory lateralization in pain subjective perception for noxious heat stimulus

The aim of the present study was to identify and characterize hemispheric lateralization for pain intensity perception. A sample of 351 healthy volunteers was tested by the immersion of the right hand for 10 s followed by the same test for the left hand (RL group; n = 199) or in a random sequence (RND group; n = 152) into a water bath (48°C, 15 s). Pain intensity was self-reported by the Visual Analogue Scale (VAS). The motor hemispherical Lateralization Index (LI) was obtained by the Edinburgh Inventory. Gender, hand skin fold, interstimulus time and menstrual cycle data in case of female subjects were recorded. The sample, 60.7% females and 39.3% males, 20.4 &#45 0.18 (mean &#45 SEM) years old, showed 92.1% right-handed subjects. Left hand VAS was significantly higher than right hand VAS for RL (7.24 &#45 1.31 vs 6.74 &#45 1.52; p < 0.01) and RND (7.24 &#45 0.82 vs 6.73 &#45 1.25; p < 0.01) both for right- and left-handed subjects. A low but significant correlation for VAS scores and LI was found ( r = 0.14; p < 0.05 or r = 0.18; p < 0.05, for left or right hand, respectively). Skin fold was statistically similar in both hands ( p > 0.05) being highly correlated with each other ( r = 0.68; p < 0.05). Pain subjective perception was not correlated to interstimulus time ( r = -0.01; p > 0.05). Females showed significantly higher values than males for both left and right hand VAS scores. Periovulatory phase VAS value was significantly higher than luteal phase VAS only for the right hand test (7.57 &#45 0.20 vs 6.47 &#45 0.33; p < 0.01). The results of the present study suggest a lateralization of pain intensity perception to the right hemisphere not correlated with the motor hemispheric lateralization.     

Rapid elevations in both steroid hormones and vocal signaling during playback challenge: a field experiment in Gulf toadfish

It is well known that plasma androgens are rapidly released in response to aggressive or sexual stimuli in a broad array of vertebrates. However, experimental work on behavioral functions of rapid androgen elevation is rare. A combination of field-based behavioral experiments and lab-based neuroendocrinological approaches is beginning to show how steroid hormones rapidly regulate the expression of vocal communication signals in Gulf toadfish (Opsanus beta). Male toadfish emit multiharmonic "boatwhistles" and shorter-duration, broadband "grunts" during intraspecific communication. Neurophysiology experiments demonstrate that androgens and glucocorticoids rapidly modify vocal motor patterning in male toadfish. In this study, we simulated territorial intrusions (vocal "challenges") with acoustic playbacks to toadfish in the field, and observed simultaneous, rapid (within 5-20 min) changes in vocalizations and steroid hormones. Both plasma androgens and vocal activity increased following the presentation of pure tones that mimic the duration of natural boatwhistles (275 ms), while they remained unchanged following playbacks of tone stimuli that mimic the duration of grunts (75 ms) or the upper-range of boatwhistles (475 ms). Circulating glucocorticoids were elevated in calling vs. non-calling males but were unaffected by playback stimuli, suggesting a role in the energetics of vocalization. These results strongly suggest that one function of rapid androgen elevation in response to social challenge is to mediate similarly rapid changes in territorial vocal signaling. Given the conserved organization of neuroendocrine and vocal motor systems, rapid steroid action on vocalization mechanisms may be true of other vocal vertebrates as well, including birds and mammals.     

Epidemics in competition

When two or more epidemic agents are simultaneously present in a population, they may interact to increase or decrease each other's effectiveness. One form of interaction is competition where each agent confers immunity to the others. Such competition occurs, for example, between different strains of myxomatosis in rabbit populations. We consider some consequences of introducing competition into mathematical epidemic models. Both deterministic and stochastic simple epidemic models are examined. In either case the conclusions are similar: the faster spreading epidemic has a considerable advantage.     

Diurnal and Seasonal Cortisol,Testosterone, and DHEA Rhythms in Boys and Girls during Puberty

Diurnal and seasonal rhythms of cortisol, testosterone, and DHEA were examined, as little is known about the relationship between these rhythmicities and pubertal development. Salivary samples were obtained from 60 boys and 60 girls at approximately 07∶45, 08∶00, 08∶30, 12∶00, 16∶50, and 21∶00 h. The participants' ages ranged from 8–14 yrs, and each participant was tested three times at six‐month intervals. The study was conducted at a General Clinical Research Center (GCRC) and at the homes of the participants. All hormones showed diurnal fluctuations. The acrophase (peak time) of cortisol occurred earlier than for testosterone or DHEA and showed a seasonal effect, with the acrophase occurring earlier in spring than in summer. The cortisol acrophase also occurred later in the day for boys than for girls during later puberty. Seasonal effects were found only for cortisol with higher concentrations in the spring and summer. Cortisol concentrations were relatively stable across pubertal maturation, but significantly lower concentrations were observed at pubertal stage 3 compared to the other stages. Morning cortisol levels were also higher in boys at pubertal stage 2. Testosterone concentrations were higher in boys at pubertal stages 3 and 4, and DHEA was lower at pubertal stage 1 than 3 and 4 for both boys and girls. For the total sample, there was a positive correlation between DHEA and testosterone during early puberty (stages 1–3) but not later puberty (stages 4–5). Awakening secretory activity correlated with daytime secretory activity for testosterone and DHEA, but not for cortisol. These data provide novel chronobiological information on cortisol, testosterone, and DHEA as it relates to sexual maturation and encourage further study on both normal and abnormal endocrine rhythms.